Pseudogap-less high T$_{c}$ superconductivity in BaCo$_{x}$Fe$_{2-x}$As$_{2}$

TL;DR

This study shows that BaCo$_{x}$Fe$_{2-x}$As$_{2}$ lacks a pseudogap state across doping levels, with superconducting gaps closing at T$_{c}$, indicating a different mechanism from cuprates.

Contribution

It provides direct spectroscopic evidence that pseudogap phenomena are absent in BaCo$_{x}$Fe$_{2-x}$As$_{2}$, contrasting with cuprate superconductors.

Findings

No pseudogap observed in all doping levels.

Superconducting gaps close at T$_{c}$ in spectra.

Large-scale superconducting regions in underdoped samples.

Abstract

The pseudogap state is one of the peculiarities of the cuprate high temperature superconductors. Here we investigate its presence in BaCo$_{x}$Fe$_{2-x}$As$_{2}$, a member of the pnictide family, with temperature dependent scanning tunneling spectroscopy. We observe that for under, optimally and overdoped systems the gap in the tunneling spectra always closes at the bulk T$_{c}$, ruling out the presence of a pseudogap state. For the underdoped case we observe superconducting gaps over large fields of view, setting a lower limit of tens of nanometers on the length scale of possible phase separated regions.